added example to save frame via ffmpeg directly

test/darknetImageFfmpegTest.js

@@ -0,0 +1,35 @@
+const darknet = require('@moovel/yolo');
+const spawn = require('child_process').spawn;
+let ffmpeg = null;
+
+// ffmpeg -f rawvideo -s 768x576 -pix_fmt bgr24 -i data.modified.raw data.png
+function ffmpegPipe(dimensions, filename) {
+  if (!ffmpeg) {
+    ffmpeg = spawn('ffmpeg',
+      [
+        '-loglevel', 'warning',
+        '-f', 'rawvideo',
+        '-pix_fmt', 'bgr24', // or 'rgb24' if color channels are swapped
+        '-s', `${dimensions.width}x${dimensions.height}`,
+        '-y',
+        '-i', '-',
+        filename
+      ], {
+        stdio: ['pipe', process.stdout, process.stderr],
+      });
+    return ffmpeg.stdin;
+  } else {
+    return ffmpeg.stdin;
+  }
+}
+
+darknet.detectImage({
+  cfg: './cfg/yolo.cfg',
+  weights: './yolo.weights',
+  data: './cfg/coco.data',
+  image: './data/dog.jpg',
+}, function(modified, original, detections, dimensions) {
+  ffmpegPipe(dimensions, 'detected.png').write(modified, function() {
+    process.exit(0);
+  });
+});